DE102009056674B4 - Device and method for influencing the lateral dynamics of a motor vehicle - Google Patents

Abstract

Device for influencing the lateral dynamics of a motor vehicle, comprising: - one or more actuators (4) for wheel-specific adjustment of drive and braking torques, - a vehicle dynamics observer (2) which provides a yaw rate and/or yaw acceleration based on a reference model of the vehicle, - a pilot control (31) for generating a first control signal component for the actuator(s) (4) based on a first signal that represents a driver's request regarding the direction of travel and a second signal that represents a driver's request regarding the driving speed, - a controller (32), to which a yaw rate and/or yaw acceleration difference is connected as an input variable, which is formed from a target value and an actual value, the target value being determined by the vehicle dynamics observer (2) and the actual value being measured or determined from measured vehicle parameters, and as Output signal provides a second control signal component for the actuator(s) (4). characterized in that the basic setting of the control signal for the actuator(s) (4) takes place in the pilot control (31), whereas modeling inaccuracies and environmental influences are compensated for via the controller (32), the vehicle dynamics observer (2) receives the first signal that represents a driver's request with regard to represents the direction of travel, and the second signal, which represents a driver's request with regard to the driving speed, are connected as input variables and the vehicle dynamics observer (2) determines from this a desired movement of the vehicle in the form of the yaw rate and / or yaw acceleration, and for the pilot control (31) as input variables only the first signal, which represents a driver's request regarding the direction of travel, the second signal, which represents a driver's request regarding the driving speed, and the desired movement of the vehicle provided by the vehicle dynamics observer (2) are used to calculate a torque to be pre-controlled represented by the first control signal component; the combined control signal from the first control signal component (s1) and the second control signal component (s2) represents an additional yaw moment (MZ, TV) required to realize a desired vehicle movement through torque vectoring, and the control signal formed from the two control signal components (s1, s2) serves for this purpose , via the actuator(s) (4) on the vehicle to effect the additional yaw moment (MZ,TV) through torque vectoring and the build-up of said additional yaw moment (MZ,TV) is realized by a distribution of drive torques, a braking intervention or a combination of both.

Description

The invention relates to the field of vehicle lateral dynamics and in particular to actively influencing the yaw angle of motor vehicles. The latter is sometimes also referred to as Active Yaw or Torque Vectoring.

In particular, the invention relates to a device according to the preamble of patent claim 1 and to a method according to the preamble of patent claim 8. These are out DE 10 2006 033 635 A1 known.

Other devices and methods are out EP 1 886 864 A1 known.

Conventional open differentials enable a motor vehicle to corner by allowing different speeds on the vehicle wheels on one axle. The drive torque is transmitted evenly to both wheels. However, there are limits to the driving dynamics properties in that the traction of the wheel with better grip is limited by the wheel with less grip. This is particularly noticeable on slippery roads or when cornering quickly.

Traction and driving dynamics can be improved by means of a limited-slip differential, which at least partially couples the drive wheels to one another through friction, for example. However, the lock makes cornering more difficult, so that the vehicle tends to understeer. Adjustable differential locks combine the cornering ability of an open differential with the improved traction of a limited-slip differential. Thanks to intelligent logic that takes the respective driving condition into account, the differential is only closed to the extent required by the respective driving situation. Nevertheless, a controlled limited-slip differential is only able to make a vehicle more willing to corner in exceptional situations. The advantageous properties of a cross-lock principle can mainly only be experienced in the limit driving range. Due to its principle, a limited-slip differential cannot increase existing speed differences or transfer a larger torque to a faster rotating wheel.

Furthermore, it is generally known to influence the yaw angle of a motor vehicle through automatic braking interventions in order to improve vehicle dynamics and driving safety. However, when braking, drive energy is converted into friction losses, which is contrary to a dynamic driving style.

Torque vectoring differentials, such as those from DE 103 17 316 A1 , DE 10 2004 001 019 A1 , DE 10 2005 040 253 B3 , DE 10 2007 020 356 A1 or US 7,267,628 B2 are known, make it possible to apply higher drive torque to either a faster or slower wheel. Here, a drive torque that can in principle be specified as desired is subtracted from one wheel and added to the opposite wheel. The sum of the drive torques of the wheels on an axle remains the same, which means that the driving speed is not affected. Through torque vectoring, ie controlling the torque vectoring differential for the purpose of targeted distribution of the drive torque to the vehicle wheels, the stability of the vehicle can be improved during dynamic driving, so that the intervention of an electronic stability program (ESP) is delayed. However, as soon as the ESP detects a critical driving condition, it takes control and deactivates the torque vectoring system.

Furthermore, in all-wheel drive vehicles, it is possible to variably distribute the drive torque provided by the vehicle engine to the vehicle axles, for example via a torque vectoring differential.

A central problem with torque vectoring systems is determining the required wheel torques, i.e. the drive and braking torques on the vehicle wheels.

From the DE 10 2008 032 763 A1 In this context, it is known to use a vehicle dynamics observer to determine a target yaw rate for the vehicle and then to determine the deviation from a measured actual yaw rate. The yaw rate difference is connected to a vehicle dynamics controller, which, among other things, generates an actuating signal that enables wheel-specific drive and braking torques to be set via a torque vectoring differential and the vehicle braking system.

Based on this, the invention is based on the object of creating a robust adjustment of the wheel torques of a motor vehicle, which is characterized by a highly dynamic and harmonious response.

This object is achieved by a device for influencing the lateral dynamics of a motor vehicle according to patent claim 1 and furthermore by a method according to patent claim 8.

The control signal formed from the control signal components causes a yaw moment through torque vectoring via the actuator(s) on the vehicle. The build-up of the additional yaw moment can be realized by a distribution of drive torque, a braking intervention or a combination of both.

The pilot control component, i.e. the first control signal component, is based on variables that are noise-free, reliable and instantaneous. This makes a highly dynamic, yet harmonious intervention possible.

The second control signal component, which is generated in parallel to the first control signal component, can primarily be used to compensate for modeling inaccuracies and environmental influences.

Thanks to the pre-control, the control difference applied to the controller remains significantly lower in most cases than in a device without pre-control.

This achieves greater control stability and enables higher controller gains.

The low level of controller intervention also contributes to greater harmony in the control of the wheel torques.

Advantageous embodiments of the invention are specified in further patent claims.

The vehicle dynamics observer is preferably configured in such a way as to determine a target yaw rate and/or a target yaw acceleration using the first signal, which represents the driver's request regarding the direction of travel, and using the second signal, which represents the driver's request regarding the driving speed. Corresponding signals are used in the precontrol to generate the first control signal component. Signals required by the precontrol and the controller are only calculated once.

The reference model of the vehicle on which the vehicle dynamics observer is based is preferably a single-track model. It has been shown that this is capable of providing suitable reference variables for controlling vehicle dynamics control systems. Compared to multi-track models, the required computing effort is significantly lower. In an advantageous embodiment, variables that represent a slip angle on the front and rear axles are fed back into the vehicle dynamics observer.

To improve the quality of the control, a signal representing the driving speed can be connected to the controller as a further input variable, so that control intervention by the controller is possible depending on the driving speed.

As already explained above, the control of the wheel torques can be achieved by torque vectoring both through a targeted distribution of the drive torque to different vehicle wheels and/or vehicle axles and/or through a braking intervention. In the former case, at least one actuator in the form of a torque vectoring differential is provided on the vehicle, which can be designed in a conventional manner, for example as in the publications mentioned above. A braking intervention can be implemented using wheel brakes known to those skilled in the art.

• 1 eine schematische Darstellung der Struktur einer erfindungsgemäßen Vorrichtung zur Beeinflussung der Querdynamik eines Kraftfahrzeugs,
• 2 eine schematische Darstellung der Struktur des Fahrdynamikreglers mit Vorsteuerung und Regler,
• 3 eine Detailansicht des Fahrdynamikbeobachters, und in
• 4 eine Detailansicht der Vorsteuerung und des Reglers im Fahrdynamikregler.

The invention is explained in more detail below using an exemplary embodiment shown in the drawing. The drawing shows in:

• 1 a schematic representation of the structure of a device according to the invention for influencing the lateral dynamics of a motor vehicle,
• 2 a schematic representation of the structure of the vehicle dynamics controller with pilot control and controller,
• 3 a detailed view of the vehicle dynamics observer, and in
• 4 a detailed view of the pilot control and the controller in the vehicle dynamics controller.

In the 1 The schematically illustrated device for influencing the lateral dynamics of a motor vehicle comprises the following basic components, namely input elements 1, with which the driver's wishes with regard to direction of travel and driving speed are recorded, a vehicle dynamics observer 2, which provides certain target values in relation to the yaw behavior based on a reference model of the vehicle, a Driving dynamics controller 3, as well as one or more actuators 4 for influencing the wheel torques or the longitudinal forces on the vehicle wheels.

With the actuator(s) 4, it is possible to adjust the drive and braking torques for each wheel in order to generate a yaw moment independently of the steering. In particular, despite the vehicle wheels being in a straight-ahead position, the vehicle can yaw, ie rotate about its vertical axis. Furthermore, an additional yaw moment can be superimposed on a yaw moment caused by the steering angle of the vehicle wheels. This is preferably done by means of one or more torque vectoring differentials, which allow a higher drive torque to be applied to either a faster or slower wheel on an axle and/or to influence the distribution of the drive torque on the front and rear axles. A reduced drive torque or braking torque can also be represented by wheel brakes present on the vehicle.

The determination of the required drive and braking torques or corresponding control signals to influence the lateral dynamic driving behavior will be explained in more detail below. A combined pilot-controller approach based on an inverted single-track model is used.

The driver's wishes regarding the direction of travel can be detected using a steering wheel angle sensor. Due to the mechanical conditions of the vehicle, the steering angle δ _va on the front axle is ultimately known.

The driver's wish regarding the driving speed can be determined, for example, by evaluating the signals from an accelerator pedal sensor that detects the accelerator pedal position. Alternatively or additionally, other sensors, for example wheel speed sensors on the vehicle wheels, can also be evaluated to determine the driving speed. Corresponding signals are generally available on vehicles equipped with an anti-lock braking system or an electronic stability program.

The desired movement of the vehicle is determined from the steering wheel angle and accelerator pedal position.

How 3 shows, the driving dynamics observer 2 is provided with a first signal, which represents a steering wheel angle and thus a steering angle δ _va on the front axle, as well as a second signal xap, which represents the accelerator pedal position and thus the driving speed desired by the driver, as input variables. Based on these input variables, a yaw rate Ψ̇ _ref and/or yaw acceleration Ψ̇ _ref are continuously calculated in the vehicle dynamics observer 2 on the basis of a reference model of the vehicle and provided as output variables.

$$F_{yh}=c_{ah}\cdot {\alpha }_h$$

wobei c_av und c_ah Schräglaufsteifigkeiten an Vorder- und Hinterachse darstellen. Dabei werden die Schräglaufwinkel α_v und α_h an den jeweiligen Rädern einer Achse als gleich groß vorausgesetzt.The vehicle dynamics observer 2 contains a tire model 21, with which the lateral forces F _yv and F _yh acting on the axles are determined as follows from the slip angles α _v and α _h of the vehicle wheels on the front and rear axles. $$F_{yv}=c_{av}\cdot {\alpha }_v$$

$$F_{yH}=c_{aH}\cdot {\alpha }_H$$

where c _av and c _ah represent lateral stiffness on the front and rear axles. The slip angles α _v and α _h on the respective wheels of an axle are assumed to be the same size.

wobei l_v den Abstand zwischen Vorderachse und Fahrzeugschwerpunkt und l_h den Abstand zwischen Hinterachse und Fahrzeugschwerpunkt darstellt.Using the lateral forces of the front and rear axles F _yv and F _yh , the forces and moments acting in the vehicle's center of gravity, in particular the lateral force F _y and the yaw moment M _z , can be calculated in a further module 22. This applies in particular: $$M_Z=F_{yv}\cdot I_v+F_{yH}\cdot I_H$$

where l _v represents the distance between the front axle and the vehicle's center of gravity and l _h represents the distance between the rear axle and the vehicle's center of gravity.

In conjunction with the signal xap representing the driver's desire with regard to the driving speed, the yaw rate Ψ̇ _ref and the yaw acceleration Ψ̇ _ref can be calculated from the lateral force F _y and the yaw moment M _z by integration taking into account the geometric conditions of the vehicle in a further module 23. Furthermore, the speed in the longitudinal direction of the vehicle v _x and the speed in the transverse direction of the vehicle v _y can be calculated. For the latter applies: $$v_y={\displaystyle \int \frac{F_y}{m}-\dot{\Psi }\cdot {\nu }_x}$$

$${\beta }_h=\frac{{\nu }_y+\dot{\Psi }\cdot x_h}{{\nu }_x}$$

With the help of the variables determined in this way, the slip angles β _v and β _h on the front and rear axles can be calculated in a further module 24 as follows: $${\beta }_{\nu }=\frac{{\nu }_y+\dot{\Psi }\cdot x_{\nu }}{{\nu }_x}$$

$${\beta }_H=\frac{{\nu }_y+\dot{\Psi }\cdot x_H}{{\nu }_x}$$

$${\alpha }_h={\beta }_h$$

The signals representing the slip angles β _v and β _h on the front and rear axles are fed back in the vehicle dynamics observer 2 and are used to calculate the above-mentioned slip angles α _v and α _h as follows: $${\alpha }_{\nu }={\beta }_{\nu }-{\delta }_{va}$$

$${\alpha }_H={\beta }_H$$

The output variables of the vehicle dynamics observer 2, namely the yaw rate Ψ̇ _ref and the yaw acceleration Ψ̇ _ref, serve as input variables for the vehicle, in addition to the first signal representing the driver's request with regard to the direction of travel and the second signal, representing the driver's request with regard to the driving speed Driving dynamics controller 3, as in 4 is shown.

Furthermore, the current yaw rate Ψ̇ _is and, if necessary, the current yaw acceleration Ψ̇ _is determined from the measured parameters available on the vehicle. Corresponding signals can be provided to the vehicle dynamics controller 3, for example via a bus system.

2 shows the controller structure of the vehicle dynamics controller 3. This includes, on the one hand, a pilot control 31, in which a first control signal component s ₁ is generated for the actuator(s) 4 for wheel-specific setting of drive and braking torques. Furthermore, the vehicle dynamics controller 3 additionally includes a controller 32, which is arranged parallel to the pilot control 31 and generates a second control signal component s ₂ for the actuator(s) 4. The combined control signal from the components s ₁ and s ₂ represents the additional yaw moment required to realize the desired vehicle movement through torque vectoring M _Z,TV .

Both the pilot control 31 and the controller 32 are connected to the vehicle dynamics observer 2. The pilot control 31 receives the target yaw rate Ψ̇ _ref , the target yaw acceleration Ψ̇ _ref , the steering wheel angle and the driving speed as reference variables, while at the controller 32 the target yaw rate Ψ̇ _ref and/or the target yaw acceleration Ψ̇ _ref are used on the input side. How 2 shows, there is a difference signal at the controller 32 from the target yaw rate Ψ̇ _ref and _actual yaw rate Ψ̇ and/or target yaw acceleration Ψ̈ _ref and actual yaw acceleration Ψ̈ _is on. The control intervention in the controller 32 can in particular also take place depending on the driving speed, for which purpose the signal xap is also transmitted to the controller 32.

The combination of pilot control 31 and controller 32 in conjunction with a vehicle dynamics observer 2 allows a highly dynamic influence on the vehicle yaw rate. The basic setting of the control signal for the actuator(s) 4 takes place in the pilot control 31. Since only the driving speed and the steering wheel angle or corresponding parameters are used as input variables for calculating the reference values and the torque to be piloted and these input variables are available noise-free, reliably and without delay , torque vectoring interventions can be carried out highly dynamically. In addition, the pilot control 31 can effectively relieve the controller 32, which leads to harmonious driving behavior. The control difference present at the input of the controller 32 is significantly lower than in a vehicle dynamics controller without pilot control 31. The controller 32 is primarily used to compensate for modeling inaccuracies and environmental influences. This results in a stable system that also allows high controller gains.

The structure explained above can be deviated from, particularly with regard to the configuration of the driving dynamics observer 2 and the input elements 1, as long as it is ensured that the driving dynamics controller 3 receives signals that represent a driver's request with regard to the direction of travel and driving speed as noiselessly and without delay as possible.

To influence the lateral dynamics of a motor vehicle by adjusting drive and/or braking torques for each wheel, the procedure is preferably as follows.

By means of signals representing the driver's wishes with regard to the direction of travel and driving speed, for example a steering wheel angle specified by the driver and a driving speed specified by the driver, target values for the yaw rate and/or the yaw acceleration of the vehicle are determined using a reference model of the vehicle based on a single-track model.

A first control signal component s ₁ for the actuator(s) 4 is generated from the aforementioned driver-side input variables and/or setpoint values obtained using the reference model. The first control signal component s ₁ generally represents the main portion of an additional yaw moment M _Z,TV through torque vectoring.

A yaw rate and/or yaw acceleration difference is further formed from the target values of the reference model and from corresponding, measured or actual values determined from measured vehicle parameters.

Parallel to the generation of the first control signal component s ₁ , a second control signal component s ₂ is generated for the actuator(s) 4 from the yaw rate and/or yaw acceleration difference. This is added to the first control signal component s ₁ in order to generate the desired additional yaw moment on the vehicle.

The invention was explained in more detail above using an exemplary embodiment. However, it is not limited to this, but includes all configurations defined by the patent claims.

Reference symbol list

1

Input elements

2

Vehicle dynamics observer

3

Driving dynamics controller

4

actuator(s)

21

Tire model

22

module

23

module

24

module

31

Pilot control

32

Regulator

Fyv

Lateral force on the front axle

Fyh

Lateral force on the rear axle

Fy

Transverse force

March

Yaw moment

MZ,TV

Additional yaw moment through torque vectoring

s1

Control signal component

s2

Control signal component

xap

Driving speed signal

αv

Slip angle of the front axle

ahh

Slip angle of the rear axle

βv

Slip angle on the front axle

βh

Slip angle on the rear axle

δva

Steering angle

Ψ̇is

Actual yaw rate

Ψ̇is

Actual yaw acceleration

Ψ̇ref

Target yaw rate

Ψ̇ref

Target yaw acceleration

Claims (9)

Device for influencing the lateral dynamics of a motor vehicle, comprising: - one or more actuators (4) for wheel-specific adjustment of drive and braking torques, - a vehicle dynamics observer (2) which provides a yaw rate and/or yaw acceleration based on a reference model of the vehicle, - a pilot control (31) for generating a first control signal component for the actuator(s) (4) based on a first signal that represents a driver's request regarding the direction of travel and a second signal that represents a driver's request regarding the driving speed, - a controller (32), to which a yaw rate and/or yaw acceleration difference is connected as an input variable, which is formed from a target value and an actual value, the target value being determined by the vehicle dynamics observer (2) and the actual value being measured or determined from measured vehicle parameters, and as Output signal provides a second control signal component for the actuator(s) (4). characterized in that the basic setting of the control signal for the actuator(s) (4) takes place in the pilot control (31), whereas modeling inaccuracies and environmental influences are compensated for via the controller (32), the vehicle dynamics observer (2) receives the first signal that represents a driver request with regard to the direction of travel, and the second signal, which represents a driver's request with regard to the driving speed, are connected as input variables and the driving dynamics observer (2) determines from this a desired movement of the vehicle in the form of the yaw rate and/or yaw acceleration, and for the pilot control (31) Only the first signal, which represents a driver's request with regard to the direction of travel, the second signal, which represents a driver's request with regard to the driving speed, and the desired movement of the vehicle provided by the vehicle dynamics observer (2) can be used as input variables to calculate a torque to be pre-controlled represented by the first control signal component ; wherein the combined control signal from the first control signal component (s ₁ ) and the second control signal component (s ₂ ) represents an additional yaw moment (M _Z,TV ) required to realize a desired vehicle movement through torque vectoring, and wherein the one from the two control signal components (s ₁ , s ₂ ) is used to bring about the additional yaw moment (M _Z,TV ) via the actuator(s) (4) on the vehicle through torque vectoring and to build up said additional yaw moment (M _Z,TV ) by dividing drive torques Braking intervention or a combination of both is implemented. Device according to Claim 1 , characterized in that the vehicle dynamics observer (2) determines a target yaw rate and/or a target yaw acceleration using the first signal, which represents the driver's request with regard to the direction of travel, and the second signal, which represents the driver's request with regard to the driving speed, and corresponding signals from the feedforward control as input variables are connected. Device according to Claim 1 or 2 , characterized in that the reference model of the vehicle on which the vehicle dynamics observer (2) is based is a single-track model. Device according to one of the Claims 1 until 3 , characterized in that variables representing the slip angle are fed back in the vehicle dynamics observer (3). Device according to one of the Claims 1 until 4 , characterized in that a signal representing the driving speed is connected to the controller (32) as a further input variable and the controller (32) is configured in such a way that a control intervention takes place depending on the driving speed. Device according to one of the Claims 1 until 5 , characterized in that one or the actuator (4) is a torque vectoring differential for the variable distribution of a drive torque between different vehicle wheels and/or vehicle axles. Device according to one of the Claims 1 until 6 , characterized in that an actuator (4) is a wheel brake. Method for influencing the lateral dynamics of a motor vehicle by wheel-specific adjustment of drive and/or braking torques, in which - based on a reference model of the vehicle, setpoint values for the yaw rate and/or yaw acceleration of the vehicle are determined from recorded input variables in relation to a direction of travel and driving speed specified by the driver - a first control signal component is generated from the input variables and/or setpoints obtained using the reference model, - a yaw rate and/or yaw acceleration difference is formed from the setpoints provided by the reference model as well as from corresponding, measured or actual values determined from measured vehicle parameters, and - parallel to the generation of the first control signal component from the yaw rate and/or yaw acceleration difference, a second control signal component is generated and added to the first control signal component, the control signal formed from the components being used to adjust drive and/or braking torques on the vehicle by wheel-specific adjustment to generate an additional yaw moment, characterized in that the first control signal component is obtained from a precontrol and forms the basic setting for the control signal, whereas the second control signal component corrects modeling inaccuracies and environmental influences, a vehicle dynamics observer a first signal that represents a driver's request with regard to the direction of travel, and a second Signal, which represents a driver's request with regard to the driving speed, are connected as input variables and the driving dynamics observer determines from this a desired movement of the vehicle in the form of the yaw rate and / or yaw acceleration of the vehicle, and for the feedforward control only the first signal, which represents a driver's request with regard to the Represents the direction of travel, the second signal, which represents a driver's request with regard to the driving speed, and the desired movement of the vehicle provided by the vehicle dynamics observer are used to calculate a torque to be pre-controlled represented by the first control signal component, the combined control signal from the first control signal component (s ₁ ) and the second control signal component (s ₂ ) represents an additional yaw moment (M _Z,TV ) required to realize a desired vehicle movement by torque vectoring, and wherein the control signal formed from the two control signal components (s ₁ , s ₂ ) serves via the actuator(s). (4) to effect the additional yaw moment (M _Z,TV ) on the vehicle through torque vectoring and the build-up of said additional yaw moment (M _Z,TV ) is realized by a distribution of drive torques, a braking intervention or a combination of both. Procedure according to Claim 8 , characterized in that a steering wheel angle specified by the driver and an accelerator pedal position specified by the driver are recorded as input variables.

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